Mingli Cai

Effects of N Management on Yield and N Uptake of Rice in Central China

Abstract Efficient N fertilizer management is critical for the economic production of rice and the long-term protection of environmental quality. A field experiment was designed to study the effects of N fertilizer management practices on grain yield and N uptake of rice. The experiment was laid out in the randomized complete block design with four replications in Central China during 2008 and 2009. Five N treatments denoted as N0, N150A, N150B, N240A, and N240B, respectively, were studied. N0 represented no N application and served as a control, N150A and N150B indicated the total N application of 150 kg N ha−1 but with two different application schedules (A and B) across the early stage of rice growth. Schedule A was applied as follows: 40% basal, 30% at 10 d after transplanting (DAT) and 30% at 36 DAT (nearly at the panicle initiation stage), while schedule B was as follows: 30% at basal, 20% at 10 DAT, and 50% at 36 DAT. Similarly, N240A and N240B indicated the total N application of 240 kg N ha−1 with schedules A and B as described above. To quantify N uptake from fertilizer and soil, a 15N experiment was also conducted within the main experimental field, with micro-plots. Grain yields were significantly increased as N rates increased from 0 to 240 kg N ha−1. At the same rate, splitting N application as schedule B significantly increased the grain yield, spikelets per panicle, percentage of ripened grain, and 1 000-grain weight, compared with the N application according to schedule A. Mean rice recovery of N fertilizer by 15N tracing method ranged from 25.39% at N240A to 34.89% at N150B, however, N fertilizer residual rate in the soil ranged from 12.40% at N240A to 16.61% at N150B. About 31.5 and 28.5% of total uptake of 15N derived from basal fertilizer was absorbed at panicle initiation and heading stages, respectively. However, 65.6-92.5% of total uptake of 15N derived from topdressing fertilizer was absorbed at the heading stage. Based on yield and nitrogen recovery efficiency, splitting N application according to schedule B at the rate of 240 kg N ha−1 will be more profitable among the tested five N treatments in Central China.

Methane and Nitrous Oxide Emissions from Rice-Duck and Rice-Fish Complex Ecosystems and the Evaluation of Their Economic Significance

Rice-duck (RD) and rice-fish (RF) ecological systems are major complex planting and breeding models of rice paddy fields in southern China. Studying the methane (CH4) and nitrous oxide (N2O) emissions and their economic value from these two ecosystems can provide theoretical and practical basis for further development and utilization of these classical agricultural techniques. CH4 and N2O emissions from RD and RF ecological systems were measured in situ by using static chambers technique. Using global warming potentials (GWPs), we assessed the greenhouse effect of CH4 and N2O and their economic value. Results showed that the peaks of CH4 emission fluxes from RD and RF appeared at full tillering stage and at heading stage, and the average emission fluxes were significantly (P < 0.05) lower than that from CK. N2O fluxes remained low when the field is flooded and high after draining the water. Compared with CK, the total amount of N2O emissions was significantly (P < 0.05) higher and slightly lower than those from RD and RF, respectively. In 2006 and 2007, the total greenhouse effect of CH4 and N2O from RD and RF were 4 728.3 and 4 611 kg CO2 ha−1, 4 545 and 4 754.3 kg CO2 ha−1, respectively. The costs of greenhouse effect were 970.89 and 946.81 RMB yuan ha−1, and 933.25 and 976.23 RMB yuan ha−1, respectively, which were significant lower than those from CK (5 997.6 and 5 391.5 RMB yuan ha−1). Except for the environment cost of CH4 and N2O, the economic benefits from RD and RF were 2 210.64 and 4 881.92 RMB yuan ha−1; 3 798.37 and 5 310.64 RMB yuan ha−1, respectively, higher than those from CK. Therefore, RD and RF complex ecological planting and breeding models can effectively decrease and control CH4 and N2O emissions, and they are two of the effective strategies to reduce greenhouse gases from rice paddy fields and contribute in alleviating global warming. Thus, their adoption is important to the environment together with their economy benefits.

Identification of two Monilia species from apricot in China

Abstract Monilinia fructicola, Monilia mumecola and Monilia yunnanensis have been reported as the causal agents of brown rot disease on stone fruits in China. Up to date, these species have been identified from peach and plum, and M. mumecola has also been reported on apricot recently. To investigate whether M. fructicola and M. yunnanensis can cause brown rot disease on apricot in China, 37 isolates were collected from four orchards in Chongqing and Beijing municipalities in 2014. These isolates were divided into two phenotypes according to their distinct colony appearances. Two representative isolates of each phenotype and reference species of M. mumecola from apricot were selected for further analysis. Based on the morphological characterization and molecular identification, the two phenotypes of isolates were identified as M. fructicola and M. yunnanensis, respectively.

Different response of an elite Bt restorer line of hybrid rice (Oryza sativa L.) in adaptation to nitrogen deficiency

Transgenic Bacillus thuringiensis (Bt) rice have been reported to acquire effective resistance against the target pests; however, the insertion and expression of alien Bt genes may have some unintended effects on the growth characteristics of rice. A screen-house experiment was conducted and repeated twice to investigate the growth characteristics and Bt protein expressions in two Bt rice lines [MH63 (Cry2A*) and MH63 (Cry1Ab/Ac)], which had different Bt protein expression levels in leaves, under zero nitrogen (N0) and recommended nitrogen (NR) fertilizer applications. Compared to the counterpart MH63, MH63 (Cry2A*) under N0 experienced accelerated leaf senescence and a lower internal N use efficiency (IEN), resulting in a 23.2% decrease in grain yield and a lower accumulated biomass. These variations were revealed to be correlated to the higher ratio of the Bt protein content to the soluble protein content (BTC/SPC) with a maximum value of 4.3‰ in MH63 (Cry2A*) leaves in the late growth stage. Under NR, no differences in growth characteristics between MH63 (Cry2A*) and MH63 were found. The growth characteristics of MH63 (Cry1Ab/Ac), with a lower BTC/SPC in the late growth stage compared to MH63 (Cry2A*), were identical to those of MH63 under the two N applications. Results show that the transgenic Bt rice MH63 (Cry2A*), with a relatively higher Bt protein expression in the late growth stage, had an inferior adaptation to nitrogen deficiency compared to its non-Bt counterpart. And this inferior adaptation was found to be correlated with the higher BTC/SPC in MH63 (Cry2A*) leaves in the late growth stage.

Crop yield, P uptake and soil organic phosphorus fractions in response to short-term tillage and fertilization under a rape-rice rotation in central China

We conducted a 3-year field experiment on an Anthrosol paddy soil to investigate changes in crop yield, P uptake and soil organic phosphorus (P) fractions after 3 years of conventional tillage (CT) conversion to no-tillage (NT) under a rape - rice rotation in central China. Treatments were established following a split-plot design of a randomized complete block with tillage practice as the main plot and fertilizer as the sub-plot treatment. The yields of rape and rice ranged from 1378 to 2264 kg ha-1 and from 5895 to 9453 kg ha-1 across 3 years, respectively. Moreover, P uptake for rape and rice (aboveground) varied from 3.9 to 10.4 kg ha-1 and from 9.5 to 32.0 kg ha-1, respectively. Fertilization significantly enhanced crop yields and P uptake, but tillage did not affect the yields and P uptake. Fertilization significantly increased total P concentrations, acid phosphatase activity, Bray-1 P and labile organic P in the 0-5 cm soil layer. Compared to the CT treatments, the NT treatments had significantly higher acid phosphatase activity, total P, Bray-1 P, total organic P and organic P fractions in the 0-5 cm soil layer but lower organic P fractions in the 5-20 cm soil layer. Therefore, our results suggest that short-term NT does not enhance organic P concentrations in the 0-20 cm soil layer, and only improve P availability on the soil surface.